The present invention relates to an apparatus and method for coating a surface of a substrate to be processed such as an LCD (liquid crystal display) substrate or a semiconductor wafer with a process solution such as a developing solution.
In the manufacture of, for example, a liquid crystal display (LCD) device, a thin film of, for example, ITO (Indium Tin Oxide), an electrode pattern, etc. are formed on an LCD substrate (glass substrate). Therefore, applied is a series of processing, in which a circuit pattern, etc. is transferred in a reduced fashion onto a photo-resist by using a photolithography technology similar to that employed in the manufacture of a semiconductor device, followed by developing the circuit pattern, etc. transferred onto the photo-resist.
To be more specific, a substrate such as a rectangular LCD substrate is disposed on a spin chuck capable of a high speed rotation to coat a surface of the LCD substrate with photo-resist while rotating the substrate at a high speed, followed by selectively exposing the photo-resist to light in a light-exposure device to form a pattern. Then, the LCD substrate after the light-exposure step is disposed to face a nozzle for supplying a process solution such as a developing solution. Under this condition, the LCD substrate and the nozzle are moved relative to each other to form a film of a developing solution, which is upheaved by surface tension of the solution, on the LCD substrate, thereby to perform development for a predetermined time. Then, a deionized water or pure water is supplied to the substrate while rotating the spin chuck at a high speed so as to centrifugally remove the developing solution and, thus, to stop the developing treatment.
In the conventional process, however, a serious problem is brought about. Specifically, a substrate G disposed on a spin chuck 1 is larger than the spin chuck 1 and, thus, extends over an edge of the spin chuck 1 to form an overhanging portion, as shown in FIG. 1. Also, the overhanging portion is bent downward, and the bending degree is increased with increase in the overhanging amount. Naturally, a process solution supplied to the substrate G flows toward the periphery of the substrate, making it difficult to coat uniformly the substrate G with the process solution.
The overhanging amount can be diminished by enlarging the spin chuck 1. However, the manufacturing cost is increased if the spin chuck is enlarged. Also, when it comes to, particularly, a spin chuck of an air suction type, the enlargement of the spin chuck causes an increase in the air-sucking amount, leading to an increased possibility of dust attachment to the substrate G.
It should also be noted that, in the conventional developing process of this type, the developing solution is recovered. However, the recovered developing solution is considerably diluted with a rinsing liquid. As a result, it is difficult to adjust the concentration of the recovered developing solution. In some cases, it is impossible to reuse the recovered developing solution.